Every young actor dreams of playing the Joker, and the reason is it's a completely blank canvas but is still such an iconic character in 21st century western culture. The Joker, who started off as just a clown who pulled off some robberies, descended (is that the right word) into a visualisation of madness, and eventually terrifying psychotic violence. The Joker has been present as the arch nemesis of Batman, a character that has himself cut through his comic book origins, throughout Batman's many iterations in media, to the extent that you would be hard-pressed to find someone who couldn't identify Joker as Batman's enemy. There are not many characters in all of literature that can claim that - Sherlock Holmes and Moriarty springs to mind, but I don't even think that would be as readily available to the common consciousness.So when Heath Ledger was given the reigns, I have to admit I balked. The guy from 10 Things I Hate About You and Brokeback Mountain? A friend of mine (Oli Fenton of the tongue-in-cheek metal band Satan's Buttcheeks) said he trusted Christopher Nolan, which put me at ease - the man had made Memento, Insomnia and Batman Begins at this point, so he knew how to assemble a cast - and he was absolutely right.Ledger embodied the character with a terrifying fearlessness - a trait Ledger determined from the most important source - the script. Every decision the Joker makes in the script is motivated by a vehement rejection of a hypocritical societal structure that attaches different values to one life over another, and his need to prove this to the world, as he says to Dent in the hospital scene:

The Joker: I’m not a schemer. I try to show the schemers how pathetic their attempts to control things really are. So, when I say -- ah, come here -- when I say that you and your girlfriend was nothing personal, you know that I’m telling the truth. ...Look what I did, to this city with a few drums of gas and a couple of bullets. Hm? You know what, you know what I noticed? Nobody panics when things go according to plan. Even if the plan is horrifying. If tomorrow I tell the press that like a gang banger will get shot, or a truckload of soldiers will be blown up, nobody panics, because it’s all part of the plan. But when I say that one, little old mayor will die, well then everyone loses their minds! [Joker hands Two-Face a gun and points it at himself] Introduce a little anarchy. Upset the established order, and everything becomes chaos. I’m an agent of chaos.

This is fantastic writing, by Christopher and Jonathon Nolan, but imagine what the words looked like when they were just words on a page, before Ledger had read them. The fact that you probably read them in your head in the sinister voice he affected shows how indelible his performance was - you can probably even remember the exact way he followed the stage direction [Joker hands Two-Face a gun and points it at himself]. His complete physical self was embodied in the role.

This complete immersion in character was why he was able to improvise so memorably as he's blowing up the hospital when the actual explosive on set delayed. It's why it's so affecting when he hisses out the words "Why so serious?" to an adversary. Imagine how the Jack Nicholson, or Mark Hamill, Joker would have delivered those three words - it doesn't carry the same menace, even though both are fantastic portrayals of the character. And it makes his maniacal laugh all the more infuriating to Batman when he informs him, "You have nothing to threaten me with."Ledger won the Best Supporting Actor Oscar, and IT WASN'T JUST BECAUSE HE DIED. The Academy has often used the category to reward stellar performers in big budget tentpole movies -- Tommy Lee Jones in The Fugitive, Cuba Gooding Jr in Jerry Maguire -- and had nominated comic book action movies before - Al Pacino in Dick Treacy. And given that 2008 wasn't a vintage year in film, I don't think it's a stretch to say his was the best performance of the nominees in the category that year.

Robert Downey Jr in Chaplin [1993]

Robert Downey Junior has pretty much parked his career in being Iron Man plus a few talky roles - something I hope he grows out of once his generous contractual commitments have been completed. He is an unbelievably good natural character actor - as displayed in his career-shaping turn as Charlie Chaplin.Chaplin himself was a figure who broke all conventions. Raised in Elephant and Castle, a forgotten district of the no-go South East London, he grew to be the biggest star on the planet, and one of the very few starts who managed to bridge the transition from silent movies to 'talkies'. All the while upending stereotypes about homelessness and defending Jewish people amidst the rise of Fascism.In the film, Downey Jr encapsulates all this, while portraying the actor over a remarkably long stretch of his life. And he does more than just the impersonation, which is a trap a lot of actors fall into when portraying real people. It is not the person you are playing, it is the dramatic interpretation of the person - the actor's job is to interpret the script as written. Downey Jr gives the character pathos and joy, while delivering a beautiful physical performance that Chaplin himself would have been proud of.

Clearly Downey Jr had meticulously researched the part, along with director Richard Attenborough (who was a contemporary of Chaplin, and would likely have crossed paths during their lengthy careers), but it's the sparkling energy of his performance that lifts the films above it's own pitfalls.
Downey Jr was Oscar-nominated for the role, but lost out to Al Pacino -- the Academy likes to right it's past wrongs a lot, Scent of a Woman was far from Pacino's great performance, and is easily the weakest in a strong field.

Jim Carrey in The Truman Show [1999]

Jim Carrey's brilliant command of physical comedy is well-known, ranging from the zany (The Mask) to the cartoonish (The Grinch). He has completely dominated this type of comedy in American cinema since the mid 1990s. My favourite performance of his is in one of the most underrated films of the 1990s; his understated turn in The Truman Show.

The plot revolves around a man who is starting to discover that his whole life has been controlled by a higher power -- a megalomaniacal reality TV showrunner, who has hired actors, costume and prop departments to maintain a 24 hour facade for Truman, since the day he was born, to be live-streamed across the globe. In 1999, this idea seemed wacky enough to market as a Jim Carrey movie - now it seems outdated because it's being broadcast on television (although...).

Carrey had been hitting huge box office successes in his previous films, so it was a huge risk for him to take on what is actually a very high-minded concept film from a writer who had only one, largely unsuccessful, sci-fi credit to his name. And if IMDb trivia is to be believed (it can't always, by the way, it is editable by users!), he wanted to throw off the shackles of his "silly" movies.

And he did so with aplomb - showing that he could act with character-driven emotion as well as portray his impeccable comic timing. It would have been tempting to play the role straight down the line, but Carrey, drawing from the script, imbued Truman with a childlike wonder, and an all-to-human sense of curious exploration. There is a tinge of sadness behind his eyes in this improvised scene where Truman is just goofing around on his own in front of a mirror.

And because the character has been trapped in a huge lie, that literally everyone in his life is in on, Carrey had to juggle his paranoia with the face that he has to face his work colleagues with. And as he figures out that all the pieces of the puzzle fit together too readily (a car pulls out of the driveway, just as a jogger runs past - every fifteen minutes), he can't show his frustration too much because he doesn't know who he can trust.And when he finally does break out from the clutches of the townspeople (spoilers: it's a standalone film), his liberation feels earned. This is a triumph of the writing and the perfectly realised direction, but it's Carrey's performance throughout that has the audience engage with his journey so deeply. If he had just put his Adam Sandler pants on that day and pratted around with abandon, nobody would have given a shit once they had walked out the cinema doors: I don't imagine many people were on tenterhooks when his character in Liar Liar commandeered a stair-car and chased an aeroplane down a runway.Carrey won the Golden Globe for best actor that year, but didn't even get nominated in the Oscars: surprisingly, Roberto Bagnini won for a foreign-language film - even against Tom Hanks in a WW2 film.

So that's three great film performances, by males in leading roles in US films - I'm going to do more of these for different categories such as lead female (Charlize Theron will show up), non-US (Brendan Gleeson), television (The West Wing), ensemble casts (L.A. Confidential), career-long (De Niro, Meryl Streep) and others.

Tell me in the comments who I should mention - or what categories I should cover!